242 54 



been able to see. Strong, well-developed retractor muscles for the wheel-organ; 

 from six to seven transversal muscle bands. Size male 120 ji*, female 250 — 400 /t. 



Brachionus urceolaris O. F. M. 



Male: Cohn 1856, p. 470. 

 Weber 1888, p. 56. 

 Tab. XI, fig. 4. 



Cohn (1856, p. 470, Tab. 24, fig. 8 — 9) has given a good description and two 

 fine small figures of the male. 



He correctly states that there are no lorica and spines; a short foot; a wheel-organ 

 consisting of a ciliary wreatli, encircling a disc with long stiff setæ. No opening for the mouth; 

 no trace of alimentary canal. A testis with stiff walls, which most probably are of muscular 

 structure. A penis almost of the length of the foot. The canal and the opening of it carries 

 cilia. The foot is annulated and carries two small toes. Foot glands present. Lateral canals with 

 vibratile tags and a contractile vesicle. A brain with a red eye. Above the testis a mass 

 of opaque grains, regarded either as part of the sexual organs, or as a remnant of the yolk. 



Weber (1888, p. 56, PI. 35, fig. 2 and 1898, p. 678, PI. 23, fig. 20) has figured 

 the male; he has only had one single specimen. He especially pays attention to the 

 following fact: 



"Si les mâles n'ont pas de cuirasse complètement formée comme la femelle, ils ont ce- 

 pendant une enveloppe chitineuse analogue" une cuirasse modifiée, qui n'avait pas encore été 

 mentionnée. C'est une cuticule beaucoup plus dure que celle des autres mâles, observés 

 jusqu'ici. Weber has not had occasion to see the vibratile tags of the excretorj' canals. There 

 is no contractile vesicle, but prostata glands. 



With regard to tlie wheel-organ Weber says: "Je n'ai pu distinguer les couronnes ciliaires 

 de la femelle; cinq lobes seulement se montraient à différentes hauteurs. De chaque côté, on 

 voit deux petits cônes, surmontés d'im long cil tactile et plusieurs touffes ciliaires." 



B. urceolaris Ehrbg. var. riihens Ehrbg. Description. Body as in B. pala, not 

 so hyaline; lorica consisting of a dorsal and a ventral plate; the first-named the 

 largest. The wheel-organ can be withdrawn into the lorica. No spines. Foot short, 

 consisting of only one joint; two toes which are very acute and better developed 

 than in B. pala. Seen ventrally, the wheel-organ as in the female shows a conspicuous 

 cleft ; on the disc are four cushion-shaped elevations dorsally, with strong stiff cilia, 

 and more ventrally a single cushion with a bunch of bristles; on the disc further 

 two, perhaps four strong setæ. The brain is very large. With regard to rudiment 

 of alimentary canal, antennæ, lateral canals, testis, penis and foot glands I find no 

 differences between B. riibens and B. pala. The longitudinal muscles have a some- 

 what different course. The penis may be protruded just as in B. pala; it is then of 

 quite the same form and composition; on the figure it is shown withdrawn. Size 

 male 120— 130;(t, female 250— 280 /f. 



B. riibens, which is often regarded as a variety of B. urceolaris, (not by Rous- 

 SELET 1907, p. 151) has the peculiar custom almost alwaj's to fasten itself to the 

 carapace of the parthenogenetic generations of D. pulex, coating them with a thick 

 mantle. It is a pronounced pond form; I haye only met with it in late spring and 

 midsummer. 



